(1) Field of the Invention
The present invention relates to release systems. More particularly, the present invention relates to controlled corrosion release systems for underwater payloads.
(2) Description of the Prior Art
A number of applications require the placement of a payload in an underwater environment. Typically, the payload is buoyant and is attached to an anchor that holds the payload underwater. After a period of time, the payload is released from the anchor and rises to the surface. The well-known options for securing and subsequently releasing the payloads from the anchor in these applications include constant corrosion releases, mechanical releases utilizing a motor/actuator, or burn wire releases.
A constant corrosion release starts corroding the moment it is emplaced. Therefore, with this method the actual moment of release cannot be changed. Also, the mechanical strength of the restraining member that forms the release will necessarily decrease, as this restraining member must also be the corroding member. Additionally, the corrosion release cannot be guaranteed to release when desired.
A mechanical release requires more volume for an actuator and more complexity and cost. This type of release will have a lower reliability and does not have an efficient or practical fail-safe release feature should the mechanical release fail to operate. A burn-wire release burns through a tensioned wire, releasing the pay load item. This method requires a more complex mechanism overall and has limited holding strength. As in the case of a mechanical release, a burn wire release does not have a fail-safe release feature. If the mechanism for initiating the burn-wire fails, the payload will not be released.
Thus, a need has been recognized in the state of the art to provide a release mechanism that reduces both complexity and costs, while increasing reliability. There is also a need to provide a release mechanism that includes a fail-safe feature, i.e., the release mechanism should eventually release the payload regardless if the primary release mechanism fails.
As in the case of a mechanical or burn-wire release, the payloads need to be released within a predetermined time after the release command is issued. Additionally, there is a need to provide a release mechanism that requires a small amount of volume to implement, while being able to vary the holding strength of the mechanism.